RESUMEN
CUO246, a novel DNA gyrase/topoisomerase IV inhibitor, is active in vitro against a broad range of Gram-positive, fastidious Gram-negative, and atypical bacterial pathogens and retains activity against quinolone-resistant strains in circulation. The frequency of selection for single step mutants of wild-type S. aureus with reduced susceptibility to CUO246 was <4.64 × 10-9 at 4× and 8× MIC and remained low when using an isogenic QRDR mutant (<5.24 × 10-9 at 4× and 8× MIC). Biochemical assays indicated that CUO246 had potent inhibitory activity against both DNA gyrase (GyrAB) and topoisomerase IV (ParCE). Furthermore, CUO246 showed rapid bactericidal activity in time-kill assays and potent in vivo efficacy against S. aureus in a neutropenic murine thigh infection model. These results suggest that CUO246 may be useful in treating infections by various causative agents of acute skin and skin structure infections, respiratory tract infections, and sexually transmitted infections.
Asunto(s)
Girasa de ADN , Topoisomerasa de ADN IV , Animales , Ratones , Girasa de ADN/genética , Topoisomerasa de ADN IV/genética , Inhibidores de Topoisomerasa II/farmacología , ADN Bacteriano , Staphylococcus aureus , Pruebas de Sensibilidad Microbiana , Antibacterianos/farmacología , Antibacterianos/uso terapéuticoRESUMEN
Chlorocyclopropanes (CCPs) conjugated to alk-yn-enes occur in a unique family of polyketide natural products from marine sponges. Synthesis of several optically enriched analogs of CCPs and measurement of their UV-vis spectra and electronic circular dichroism (ECD) spectra reveal unusually strong hyperconjugation that constrains and aligns the cyclopropyl C-C bond with the π-plane of the distal ene-bond. This alignment imposes a barrier to rotation of at least 5.0 kcal·mol-1 . Comparison of red-shifted Cotton effects in chiral CCPs show the barrier is independent of alkene substituent and establishes an empirical rule for assignment of other CCP-containing natural products.
Asunto(s)
Alquenos/química , Alquinos/química , Dicroismo Circular , Ciclopropanos/química , Simulación de Dinámica Molecular , Espectrofotometría Ultravioleta , Halogenación , Conformación MolecularRESUMEN
Herein, we describe the discovery and optimization of a novel series that inhibits bacterial DNA gyrase and topoisomerase IV via binding to, and stabilization of, DNA cleavage complexes. Optimization of this series led to the identification of compound 25, which has potent activity against Gram-positive bacteria, a favorable in vitro safety profile, and excellent in vivo pharmacokinetic properties. Compound 25 was found to be efficacious against fluoroquinolone-sensitive Staphylococcus aureus infection in a mouse thigh model at lower doses than moxifloxacin. An X-ray crystal structure of the ternary complex formed by topoisomerase IV from Klebsiella pneumoniae, compound 25, and cleaved DNA indicates that this compound does not engage in a water-metal ion bridge interaction and forms no direct contacts with residues in the quinolone resistance determining region (QRDR). This suggests a structural basis for the reduced impact of QRDR mutations on antibacterial activity of 25 compared to fluoroquinolones.
Asunto(s)
Antibacterianos/farmacología , Girasa de ADN/metabolismo , Topoisomerasa de ADN IV/antagonistas & inhibidores , Diseño de Fármacos , Fluoroquinolonas/farmacología , Staphylococcus aureus/efectos de los fármacos , Inhibidores de Topoisomerasa II/farmacología , Animales , Antibacterianos/química , Farmacorresistencia Bacteriana/efectos de los fármacos , Ratones , Inhibidores de Topoisomerasa II/químicaRESUMEN
The first total synthesis of the cytotoxic marine macrolide enigmazole A has been completed in 22 steps (longest linear sequence). The sensitive, densely functionalized 2,4-disubstituted oxazole fragment was constructed using an efficient Negishi-type coupling of an oxazol-2-ylzinc reagent formed directly from the parent ethyl 2-iodooxazole-4-carboxylate by zinc insertion. Other key steps include a hetero-Diels-Alder cycloaddition to form the central embedded pyran ring, a Wittig reaction to unite Eastern and Western hemispheres, and a ring size-selective Keck macrolactonization.
Asunto(s)
Citotoxinas/síntesis química , Macrólidos/síntesis química , Compuestos Organofosforados/síntesis química , Oxazoles/química , Poríferos/química , Animales , Citotoxinas/química , Macrólidos/química , Estructura Molecular , Compuestos Organofosforados/química , Oxazoles/síntesis químicaRESUMEN
Analogues of the antifungal marine natural product (E)-dysidazirine were prepared and evaluated in broth ro-dilution assays against a panel of fungal pathogens. A simple structure-activity relationship was developed which provides insight into the mechanism of action of long-chain 2H-azirine carboxylates.
Asunto(s)
Antifúngicos/síntesis química , Antifúngicos/farmacología , Azirinas/química , Ácidos Carboxílicos/síntesis química , Ácidos Carboxílicos/farmacología , Ésteres , Pruebas de Sensibilidad MicrobianaRESUMEN
Since their discovery over 5 decades ago, quinolone antibiotics have found enormous success as broad spectrum agents that exert their activity through dual inhibition of bacterial DNA gyrase and topoisomerase IV. Increasing rates of resistance, driven largely by target-based mutations in the GyrA/ParC quinolone resistance determining region, have eroded the utility and threaten the future use of this vital class of antibiotics. Herein we describe the discovery and optimization of a series of 4-(aminomethyl)quinolin-2(1H)-ones, exemplified by 34, that inhibit bacterial DNA gyrase and topoisomerase IV and display potent activity against ciprofloxacin-resistant Gram-negative pathogens. X-ray crystallography reveals that 34 occupies the classical quinolone binding site in the topoisomerase IV-DNA cleavage complex but does not form significant contacts with residues in the quinolone resistance determining region.
Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana/efectos de los fármacos , Fluoroquinolonas/farmacología , Bacterias Gramnegativas/efectos de los fármacos , Inhibidores de Topoisomerasa II/farmacología , Antibacterianos/síntesis química , Antibacterianos/metabolismo , Antibacterianos/toxicidad , Sitios de Unión , Línea Celular Tumoral , Girasa de ADN/metabolismo , Topoisomerasa de ADN IV/antagonistas & inhibidores , Topoisomerasa de ADN IV/química , Fluoroquinolonas/síntesis química , Fluoroquinolonas/metabolismo , Fluoroquinolonas/toxicidad , Bacterias Gramnegativas/enzimología , Humanos , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Relación Estructura-Actividad , Inhibidores de Topoisomerasa II/síntesis química , Inhibidores de Topoisomerasa II/metabolismo , Inhibidores de Topoisomerasa II/toxicidadRESUMEN
Muironolide A, a new chemical entity with an unprecedented chlorinated hexahydro-1H-isoindolone skeleton, was isolated in only 90 microg yield from the same marine sponge, Phorbas sp. that also provided phorboxazoles A and B. The structure was solved by interpretation of NMR data obtained at 600 MHz with a 1.7 mm cryo-microprobe in combination with FTMS, exciton coupled CD, and stereochemical correlation with authentic standards prepared by Reformatsky reaction of (-)-(1R,2S)-2-chloro-1-cyclopropanecarboxaldehyde. The absolute configuration of the chlorocyclopropane ring in 1 is opposite to that of co-occurring phorbasides A-F. Muironolide A is the first described macrolide bearing an esterified trichloromethyl carbinol, and may be produced by a cyanobacterium that also makes phorbasides.
Asunto(s)
Isoindoles/química , Macrólidos/química , Poríferos/química , Animales , Isoindoles/aislamiento & purificación , Macrólidos/aislamiento & purificación , Modelos Moleculares , Resonancia Magnética Nuclear Biomolecular/métodosRESUMEN
Drug-resistant Gram-negative bacteria are of increasing concern worldwide. Novel antibiotics are needed, but their development is complicated by the requirement to simultaneously optimize molecules for target affinity and cellular potency, which can result in divergent structure-activity relationships (SARs). These challenges were exemplified during our attempts to optimize inhibitors of the bacterial enzyme CoaD originally identified through a biochemical screen. To facilitate lead optimization, we developed mass spectroscopy assays based on the hypothesis that levels of CoA metabolites would reflect the cellular enzymatic activity of CoaD. Using these methods, we were able to monitor the effects of cellular enzyme inhibition at compound concentrations up to 100-fold below the minimum inhibitory concentration (MIC), a common metric of growth inhibition. Furthermore, we generated a panel of efflux pump mutants to dissect the susceptibility of a representative CoaD inhibitor to efflux. These approaches allowed for a nuanced understanding of the permeability and efflux liabilities of the series and helped guide optimization efforts to achieve measurable MICs against wild-type E. coli.
Asunto(s)
Antibacterianos/aislamiento & purificación , Antibacterianos/farmacología , Escherichia coli/efectos de los fármacos , Escherichia coli/enzimología , Metabolómica/métodos , Nucleotidiltransferasas/antagonistas & inhibidores , Antibacterianos/síntesis química , Espectrometría de Masas , Pruebas de Sensibilidad Microbiana , Relación Estructura-ActividadRESUMEN
In the preceding manuscript [ Moreau et al. 2018 , 10.1021/acs.jmedchem.7b01691 ] we described a successful fragment-based lead discovery (FBLD) strategy for discovery of bacterial phosphopantetheine adenylyltransferase inhibitors (PPAT, CoaD). Following several rounds of optimization two promising lead compounds were identified: triazolopyrimidinone 3 and 4-azabenzimidazole 4. Here we disclose our efforts to further optimize these two leads for on-target potency and Gram-negative cellular activity. Enabled by a robust X-ray crystallography system, our structure-based inhibitor design approach delivered compounds with biochemical potencies 4-5 orders of magnitude greater than their respective fragment starting points. Additional optimization was guided by observations on bacterial permeability and physicochemical properties, which ultimately led to the identification of PPAT inhibitors with cellular activity against wild-type E. coli.
Asunto(s)
Antibacterianos/farmacología , Inhibidores Enzimáticos/farmacología , Proteínas de Escherichia coli/antagonistas & inhibidores , Compuestos Heterocíclicos con 2 Anillos/farmacología , Nucleotidiltransferasas/antagonistas & inhibidores , Antibacterianos/síntesis química , Antibacterianos/química , Antibacterianos/metabolismo , Bencimidazoles/síntesis química , Bencimidazoles/química , Bencimidazoles/metabolismo , Bencimidazoles/farmacología , Sitios de Unión , Descubrimiento de Drogas , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/metabolismo , Escherichia coli/efectos de los fármacos , Escherichia coli/enzimología , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Compuestos Heterocíclicos con 2 Anillos/síntesis química , Compuestos Heterocíclicos con 2 Anillos/química , Compuestos Heterocíclicos con 2 Anillos/metabolismo , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Mutación , Nucleotidiltransferasas/química , Nucleotidiltransferasas/genética , Nucleotidiltransferasas/metabolismo , Unión Proteica , Pirimidinonas/síntesis química , Pirimidinonas/química , Pirimidinonas/metabolismo , Pirimidinonas/farmacología , Triazoles/síntesis química , Triazoles/química , Triazoles/metabolismo , Triazoles/farmacologíaRESUMEN
The discovery and development of new antibiotics capable of curing infections due to multidrug-resistant and pandrug-resistant Gram-negative bacteria are a major challenge with fundamental importance to our global healthcare system. Part of our broad program at Novartis to address this urgent, unmet need includes the search for new agents that inhibit novel bacterial targets. Here we report the discovery and hit-to-lead optimization of new inhibitors of phosphopantetheine adenylyltransferase (PPAT) from Gram-negative bacteria. Utilizing a fragment-based screening approach, we discovered a number of unique scaffolds capable of interacting with the pantetheine site of E. coli PPAT and inhibiting enzymatic activity, including triazolopyrimidinone 6. Structure-based optimization resulted in the identification of two lead compounds as selective, small molecule inhibitors of bacterial PPAT: triazolopyrimidinone 53 and azabenzimidazole 54 efficiently inhibited E. coli and P. aeruginosa PPAT and displayed modest cellular potency against the efflux-deficient E. coli Δ tolC mutant strain.
Asunto(s)
Antibacterianos/farmacología , Inhibidores Enzimáticos/farmacología , Proteínas de Escherichia coli/antagonistas & inhibidores , Compuestos Heterocíclicos con 2 Anillos/farmacología , Nucleotidiltransferasas/antagonistas & inhibidores , Antibacterianos/síntesis química , Antibacterianos/química , Antibacterianos/metabolismo , Bencimidazoles/síntesis química , Bencimidazoles/química , Bencimidazoles/metabolismo , Bencimidazoles/farmacología , Sitios de Unión , Descubrimiento de Drogas , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/metabolismo , Escherichia coli/efectos de los fármacos , Escherichia coli/enzimología , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Compuestos Heterocíclicos con 2 Anillos/síntesis química , Compuestos Heterocíclicos con 2 Anillos/química , Compuestos Heterocíclicos con 2 Anillos/metabolismo , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Nucleotidiltransferasas/química , Nucleotidiltransferasas/metabolismo , Unión Proteica , Pseudomonas aeruginosa/efectos de los fármacos , Pseudomonas aeruginosa/enzimología , Pirimidinonas/síntesis química , Pirimidinonas/química , Pirimidinonas/metabolismo , Pirimidinonas/farmacología , Triazoles/síntesis química , Triazoles/química , Triazoles/metabolismo , Triazoles/farmacologíaRESUMEN
Seven new brominated ene-yne tetrahydrofurans (THFs), mutafurans A-G, were isolated from the Bahamian sponge Xestospongia muta. The absolute configuration of the natural products was assigned as (5R,8S) by interpretation of the Cotton effect arising from weak perturbation of an ene-yne chromophore by a propargylic THF ring.
Asunto(s)
Furanos/química , Hidrógeno/química , Xestospongia/química , Animales , Bromo/química , Dicroismo Circular , Ésteres/química , Ácidos Grasos Insaturados/química , Espectroscopía de Resonancia Magnética , Estructura MolecularRESUMEN
The total synthesis and evaluation of a key systematic series of vinblastines that incorporate the first deep-seated changes to the substituent at C4 are detailed. The synthetic approach features an expanded and redefined scope of a 1,3,4-oxadiazole [4 + 2]/[3 + 2] cycloaddition cascade in which electronically mismatched electron-deficient trisubstituted alkenes and unactivated trisubstituted alkenes were found to productively initiate the cycloaddition cascade with tethered electron-deficient 1,3,4-oxadiazoles. Such cycloaddition cascades were used to directly introduce altered C4 substituents, providing the basis for concise total syntheses of a series of C4 modified vindolines and their subsequent single-step incorporation into the corresponding synthetic vinblastines in routes as short as 8-12 steps. Evaluation of the synthetic vinblastines revealed a surprisingly large impact and role of the C4 substituent on activity even though it was previously not thought to intimately interact with the biological target tubulin. Only the introduction of a C4 methyl ester, a constitutional isomer of vinblastine in which the carbonyl carbon and ester oxygen of the C4 acetate are transposed, provided a synthetic vinblastine that matched the potency of the natural product. In contrast, even introduction of a C4 acetamide or N-methyl carboxamide, which incorporate single heavy atom exchanges (amide NH for ester oxygen) in vinblastine or the C4 methyl ester, provided compounds that were ≥10-fold less active than vinblastine. Other C4 acetate replacements, including a C4 amine, carboxylic acid, hydroxymethyl or acetoxymethyl group, led to even greater reductions in potency. Even replacement of the C4 acetoxy group or its equally active C4 methyl ester with an ethyl or isopropyl ester led to 10-fold or more reductions in activity. These remarkable trends in activity, which correlate with relative tubulin binding affinities, retrospectively may be ascribed to the role the substituent serves as a H-bond acceptor for α-tubulin Lys336 and Asn329 side chains at a site less tolerant of a H-bond donor, placing the methyl group of the C4 acetate or C4 methyl ester in a spatially restricted and well-defined hydrophobic half pocket created by a surrounding well-ordered loop. This remarkable impact of the C4 substituent, its stringency, and even the magnitude of its effect are extraordinary, and indicate that its presence was selected in Nature to enhance the effects of vinblastine and related natural products.
RESUMEN
A powerful tandem [4 + 2]/[3 + 2] cycloaddition cascade of 1,3,4-oxadiazoles initiated by a transannular [4 + 2] cycloaddition is detailed. An impressive four rings, four carbon-carbon bonds, and six stereocenters are set on each site of the newly formed central six-membered ring in a cascade thermal reaction that proceeds at temperatures as low as 80 °C. The resulting cycloadducts provide the basis for the synthesis of unique analogues of vinblastine containing metabolically benign deep-seated cyclic modifications at the C3/C4 centers of the vindoline-derived subunit of the natural product.
Asunto(s)
Oxadiazoles/química , Vinblastina/síntesis química , Ciclización , Estructura Molecular , Estereoisomerismo , Vinblastina/químicaRESUMEN
Three new omega-halogenated long-chain 2H-azirines were isolated from the sponge Dysidea fragilis. Their structures revealed heterogeneity in both the composition of the terminal 1,1-dihalo-vinyl group and enantiomeric ratios at C2 of the azirine-2-carboxylate ester terminus. Azirine-2-carboxylate esters were shown to racemize spontaneously. A hypothesis is proposed for the biosynthesis of the azirinecarboxylate family of natural products that involves enzyme-catalyzed free radical halogenation followed by elimination of hydrohalic acid.
Asunto(s)
Azirinas/química , Factores Biológicos/química , Dysidea/química , Animales , Apoptosis/efectos de los fármacos , Azirinas/aislamiento & purificación , Azirinas/farmacología , Factores Biológicos/aislamiento & purificación , Factores Biológicos/farmacología , Línea Celular Tumoral , Ensayos de Selección de Medicamentos Antitumorales , Halogenación , Humanos , Pruebas de Sensibilidad Microbiana , Estructura Molecular , EstereoisomerismoRESUMEN
A short, flexible synthesis of the marine natural product (2 R)-(Z)-dysidazirine (-)-1 has been completed. (-)-1 shows significant antifungal activity across a panel of seven human pathogens, whereas the structural analogue (-)-2, featuring a terminal tert-butyl group, is essentially inactive.
Asunto(s)
Antifúngicos/síntesis química , Antifúngicos/farmacología , Azirinas/síntesis química , Azirinas/farmacología , Antifúngicos/química , Azirinas/química , Hongos/efectos de los fármacos , EstereoisomerismoRESUMEN
Five new cytotoxic macrolide glycosides phorbasides A-E (3-7), each possessing a macrolide ring appended to a rare ene-yne-trans-2-chlorocyclopropane, were isolated from the same Western Australian sponge (Phorbas sp.) that provided phorboxazoles A and B. The structures of 3-7 were solved by analysis of spectroscopic data including NMR, MS, and CD. A synthesis of methyl 2-O-methyl-alpha-L-evalose from L-rhamnose was completed and used for configurational assignment of the sugar residue in 3. Acid-catalyzed methanolysis of 3 followed by two-step derivatization of the liberated O-methyl glycoside gave a vicinal 4-O-naphthoyl/tertiary 3-N-(2-aminonaphthyl)carbamate derivative that exhibited exciton coupled CD identical with that of the derivative prepared from synthetic 1,2- O-dimethyl-alpha-L-evalose.
Asunto(s)
Ciclopropanos/química , Glicósidos/química , Macrólidos/química , Poríferos/química , Animales , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Dicroismo Circular/métodos , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Macrólidos/aislamiento & purificación , Macrólidos/farmacología , Conformación MolecularRESUMEN
Rhizochalins C and D ( 1, 2), new representatives of two-headed glycosphingolipids, were isolated from the sponge Rhizochalina incrustata. Rhizochalin D is an unexpected C 29 homologue of the canonical C 28 dimeric sphingolipid structures. Their structures including absolute configurations were established using spectroscopic data, micromolar-scale Baeyer-Villiger oxidation, and LCMS interpretation of the products. Application of the latter method leads to a revision of the structure of oceanapiside and placement of the keto group at C-18 rather than C-11.
Asunto(s)
Glucolípidos/química , Glicoesfingolípidos/química , Glicoesfingolípidos/aislamiento & purificación , Poríferos/química , Animales , Estructura Molecular , Resonancia Magnética Nuclear BiomolecularRESUMEN
[reaction: see text] Dichlorocyclopropanation of (-)-O-menthyl acrylate under conditions of phase-transfer catalysis (CHCl3, KOH, tetramethylammonium bromide), with sonication, gives excellent yields (85-94%) of the corresponding dichlorocyclopropanecarboxylate ester compared to thermal conditions (90 degrees C, 56%). No diastereoselectivity was observed, but one isomer was isolated pure by fractional crystallization. The measured kinetic isotope effect (initial rate (CHCl3)/rate (CDCl3) approximately 1.7) suggests deprotonation of CHCl3 as the rate-limiting step.